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VII. Router Diagnostics

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Port Mirroring on DrayTek Routers

Products:
Vigor 2135ax
Vigor 2620Ln
Vigor 2760
Vigor 2762
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Keywords:
ethereal
packet trace
port mirror
wireshark

Most of the current DrayTek routers are capable of mirroring packets from the router's switch ports to a specified LAN port which can then be used with packet capture utilities or monitoring software such as the DrayTek SmartMonitor utility.

This is a switch function and on routers with in-built wireless, it is not possible for the port mirroring facility to mirror wireless traffic to the specified mirror port. In that scenario, we recommend using a separate access point.

Vigor 2820, Vigor IPPBX 2820


On the Vigor 2820 series including the Vigor IPPBX 2820, the router can mirror traffic from LAN ports and WAN2 to a specified port either via the telnet or web interface of the router.

Due to the way the Vigor 2820's hardware is designed; when a port is set up to operate as a mirror port, it can then only receive traffic and will otherwise lose network access.

Disable the Port Mirror facility via the web interface so that the mirror port can operate normally as a LAN port again.

Web Interface

  • Go to [LAN] > [LAN Port Mirror]
  • Set Port Mirror to Enable
  • Select the Mirror Port which will be the port listening to the rest of the network
  • Tick which ports the router will be listening to under the Mirrored Port section

 

Telnet

  • Access the router's telnet interface by accessing the command prompt and entering "telnet 192.168.1.1" (substitute 192.168.1.1 with your router's IP)
  • If Telnet is unavailable in Windows, please check this guide or use Putty terminal software
  • At the telnet prompt, log into the router
  • This is the syntax for the "port sniff" command, which controls port mirroring via telnet:


> port sniff status - will show the status of the monitor port facility
> port sniff port - this will show the ports available to use as the mirror port
> port sniff txrx - this will show the ports available to mirror. This can also be used to mirror WAN2 traffic on some routers
> port sniff on - enables the port mirror facility
> port sniff off - disables the port mirror facility
> port sniff restart - restarts the switch to apply changes required to activate port mirroring.


Telnet Example 1

In this example, Port 4 will be set as the mirror port and Ports 1, 2 and 3 will be set as the listening ports:

> port sniff port p4
> port sniff txrx p1 p2 p3
> port sniff status
> port sniff restart
> port sniff on


Telnet Example 2

In this example, Port 4 will be set as the mirror port and Port 1 and WAN2 will be set as the listening ports:

> port sniff port p4
> port sniff txrx p1 WAN2
> port sniff status
> port sniff restart
> port sniff on

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First Published: 23/12/2013
Last Updated: 22/04/2021